Sensitization of photographic emulsions



April 3, 1956 J. WARREN SBNSITIZATION OF PHOTOGRAPHIC EMULSIONS FiledApril 26, 1952 2 Sheets-Sheet 1 COIIHFOL I l l l I l 10 .3'0 40 6o ea.90

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I N V EN TOR.

Jan. Mr ew,

BY Myw ATTORNEYS.

April 3, 1956 J. WARREN 2,740,713

SENSITIZATION OF PHOTOGRAPHIC EMULSIONS Filed April 26, 1952 2Sheets-Sheet 2 r/OEL MWFfE/V,

QTTORNE'YS.

United States Patent SENSITIZATION 0F PHOTOGRAPHIC EMULSIONS JoelWarren, Chevy Chase, Md.

Application April 26, 1952, Serial No. 284,506

17 Claims. (Cl. 95-7) This invention relates to the sensitization ofphotographic emulsions and to the modification of certain of theirproperties.

The sensitization of silver halide emulsions is known. There are anumber of chemical agents by means of which the speed and usually thegamma of the emulsion may be increased.

It is an object of the present invention to provide a method foraccelerating the rate of development of exposed silver halide-gelatinemulsion. Another object is to provide a developer containing asensitizing agent whereby the state of development is accelerated. Yetanother object of the invention is the provision of an emulsioncontaining a sensitizing agent. Still another object of the inventioninvolves the provision of an agent which may be applied to an ordinaryemulsion at any time prior to fixation which will increase thesensitivity and rate of development, as well as the gamma of theemulsion.

These and other objects of the invention which will be pointed out ingreater detail hereinafter, or which will be apparent to one skilled inthe art upon reading these specifications, I accomplish by that seriesof method steps and by that developer, and by that emulsion, of which Ishall now disclose certain exemplary embodiments.

Reference is made to the drawings forming a part hereof, and in which:

Figure 1 is a graph showing the eifect of an addition of the inventionto a developer of the rate of development;

Figures 2A to 2F inclusive are graphs showing the effect of treating anemulsion prior to exposure on the sensitivity;

Figure 3 shows the effect of development of ordinary emulsions indevelopers containing an agent according to my invention.

I have found that protamines (a class of strongly basic proteins of lowmolecular weight) have an extraordinary sensitizing effect on silverhalide emulsions. The protamines are a class of highly basic, watersoluble compounds found in nature in combination with nucleic acids, andthey are derived commercially from the sperm of several species of fish.The structural formula of protamines is unknown. They have anisoelectric point in the region of 12.0 and combine with a large numberof other proteins to form complexes whose solubility is related to thesalt concentration. One of these protamines, i. e., salmine, which isthe protamine derived from the salmon, according to available datacontains seven amino acids and has a molecular weight of about 8000.While all of the protamines appear to have the qualities necessaryaccording to the present invention, I have found extremely suitable theprotamines derived from the salmon (salmine) or from the herring(clupein).

I have found that contact with a protamine solution not only acceleratesdevelopment, but also increases the density for a given exposure. Thisacceleration in development and this intensification may be demonstratedat all wave lengths which will produce a latent image on a photographicemulsion. I have found that images resulting from exposure to X-rays,electrons, visible and infrared sources are affected by the protamines.

I have determined that the accelerated development rate and increase indensity can be obtained in a number of ways. The protamine may be addedto the emulsion prior to the deposition of the emulsion on the plate.The protamine may be applied to a plate carrying on emulsion either bydipping or by means of a spray. The application of the protamine in thisway to the plate may be carried out prior to exposure, or after exposureand before development, or after development and before fixing, and inall cases the density of the plate is enhanced and the development rateis accelerated. Furthermore, I have found that the protamine may beadded to the developer, and a plate having a conventional emulsion andhaving no protamine treatment prior to development will display theresults above outlined if the developing solution contains theprotamine.

I have found also that the action of protamines on an emulsion occursover a wide range of pH. When plates were immersed in protaminesolutions buffered from pH 4.6 to pH 8.8 the activity was continued. Thereaction of the protamines with photographic emulsion is very rapid andthe effect is not apparently enhanced by an increase in the contact timebeyond a few seconds.

While the protamine may be applied in many forms I prefer to apply it inthe form of the sulfate salt.

The following examples will be illustrative of the procedures which maybe followed and of the results which will be accomplished.

Example I:25 Ilford process plates were placed on a tray andsimultaneously exposed for two seconds to an incandescent lamp. These 25plates were divided into six groups of four plates each.

The four plates of the six groups were developed in standardmethol-hydroquinone developer containing respectively no protaminesulfate, 0.005 mg./cc., 0.01 mg./cc., 0.05 mg./cc., 0.25 mg./cc., and1.25 mg./cc. of protamine sulfate The four plates which were developedin the standard developer Without protamine sulfate were developedrespectively for 20, 40, and seconds. The four plates of the remaininggroups which were developed in the developer containing protaminesulfate were developed respectively for 5, 10, 20 and 40 seconds withagitation, except that in the case of the solution containing 1.25 mg./cc. of protamine sulfate an additional interval of 2.5 seconds wastested.

In each case the developer temperature was 17.8 to 18.4 C. Each platewas plunged into an acid stop bath and hypo as rapidly as possible afterdevelopment. The densities of these plates in relation to the time ofdevelopment are plotted in Figure 1.

Under the above outlined conditions the latent period of an untreatedplate was about 25 seconds and densities in the region of 1.5 werereached in approximately 75 seconds. When the developer containedprotamine the rate of development was increased roughly in proportion tothe amount of protamine added. With 0.01 mg./cc., the toe of the normalcurve was lost and the time-density relation iapractieallya straightline relation. An increase in the concentration of protamine continuesto accelerate development so that with 1.25' mg./cc. a density of 2.0was reached in 30 seconds. Substantially instantaneous developmentoccurs at concentrations of 2.0 mg./cc. or

more.

The developer referred to above as the standard metolhydroquinone"comprises two solutions as follows:

Solution A Pot. bromide gm 12.0

Hydroquinone gm 20.0

Pot. metabisulfite gm 20.0

Water q. s cc 1000.0

Solution B Sodium hydroxide gm 40.0

Water q. s cc 1000.0

constant 0.401, relative sensitivity 122.2) and exposed to anincandescent light. The plates which had been immersed in each of thesolutions were exposed respectively for 10, 30, 60 and 90 seconds, andthen all were developed for two and one-half minutes in a standardmetolhydroquinone developer,

Protamlne Exposure Development Group gfifsg' Time Time,

mglccf seconds minutes 0. 20 10 2. 5 1v 0. 20 30 2. 5 0. 20 2. 0. 20 9D2. 5 0. 05 10 2. 5 III 0. 05 30 2. 5 0. 05 60 2. 5 0. 05 90 2. 5 0. 0110 2. 5 u 0. D1 30 2. 5 0. 01 so 2. 5 0. 01 90 2. 5 None 10 2. 5 I None30 2. 5 None 60 2. 5 None 90 2. 5

The density curve for each half of the plate was recorded on amicrophotometer and the results are plotted in Figure 2.

From this figure it will be observed that the density of theprotamine-treated emulsion always exceeds that of the control half forthe exposures tested. Similarly, the gamma of the treated plates isgreater for any given exposure.

Example 3.-Five groups of five llford process plates each were exposedfor periods of 1.0, 0.5, 0.2, 0.1 and 0.04 second to an incandescentsource. One plate of each exposure was developed for two and one-halfminutes in standard hydroquinone developer containing respectively noprotamine, 0.25 mg./cc., 0.05 mg./cc., 0.01 mg/cc. and 0.005 mg./cc. Theplate densities are plotted in Figure 3.

It will be noted that concentrations between 0.005 mg/ce. and 0.05rug/cc. result in essentially similar gamma values as compared with thecontrol. With 0.250 rug/cc. the gamma was 1.3, but the density at twoand one-half minutes was essentially the same for all theprotaminedeveloper group. Pegging was encountered with the 0.25 mg./ cc.and 0.05 mg./cc. concentration and this amounted to 12% and 10%respectively of the density for these developers. Hence, theseparticular curves in Figure 3 have been corrected for backgroundaccording to the method of Pierce and Nachtreib (Ind. Eng. Chem., Anal.Ed. 13,774, 1941).

It will be understood that throughout the specification and claims whereI have used the word plate" I intend to cover the medium upon which theemulsion is carried, whether it be glass or a film of acetate or thelike.

Furthermore, as pointed out above the method can be carried out in anumber of ways, and I therefore do not intend from the method aspect tolimit myself to any particular protamine.

It will be understood that modifications may be made without departingfrom the spirit of the invention, and I therefore do not intend to limitmyself except as set forth in the claims which follow.

Having now fully described my invention what I claim as new and desireto secure by Letters Patent, is:

1. A light sensitive silver halide photographic emulsion, containing aprotamine as a sensitizing and accelerating agent.

2. A light sensitive silver halide photographic emulsion, containing aprotamine sulfate as a sensitizing and accelerating agent.

3. A light sensitive silver halide photographic emulsion, containingsalmine as a sensitizing and accelerating agent.

4. A light sensitive silver halide photographic emulsion, containingclupein as a sensitizing and accelerating agent.

5. A photographic plate bearing a light sensitive silver halidephotographic emulsion, said emulsion having a coating thereon of clupeinserving as a sensitizing and accelerating agent.

6. In the method of making a sensitized photographic plate wherein asilver halide emulsion is deposited on a plate, the step of adding aprotamine to said silver halide emulsion before its deposition on saidplate.

7. A metol hydroquinone developer for photographic emulsions containinga protamine as a sensitizing and accelerating agent.

8. A metol hydroquinone developer for photographic emulsions, containinga protamine sulfate as a sensitizing and accelerating agent.

9. A metol hydroquinone developer for photographic emulsions containingas a sensitizing and accelerating agent a protamine selected from theclass consisting of salrnine and clupein.

10. A photographic plate bearing a light sensitive silver halidephotographic emulsion, said emulsion having a coating thereon of aprotamine, serving as a sensitizing and accelerating agent.

11. A photographic plate bearing a light sensitive silver halidephotographic emulsion, said emulsion having a coating thereon of aprotamine sulfate serving as a sensitizing and accelerating agent.

12. A photographic plate bearing a light sensitive silver halidephotographic emulsion, said emulsion having a coating thereon of salmjneserving as a sensitizing and accelerating agent.

13. The method of increasing the development speed of a photographicplate having a silver halide emulsion which has been exposed, whichincludes the steps of developing it in a metol hydroquinone developer towhich there has been added a protamine, and fixing it in a conventionalhypo fixing solution.

14. In a process of exposure, development and fixation of a silverhalide photographic emulsion, the step of coating said emulsion with aprotamine solution before said exposure.

15. In a process of exposure, development and fixation of a silverhalide photographic emulsion, the step of coating said emulsion with 1protamine solution before said fixation.

16. In a process of exposure, development and fixation of a silverhalide photographic emulsion, the step of coating said emulsion with aprotamiue solution after said exposure and before said development.

17. 1n a process of exposure, development and fixation of a silverhalide photographic emulsion, the step of coating said emulsion with aprotttrnine soluiion after said development and before said fixation.

References Cited in the file of this patent UNITED STA ES PATENTS KarrerOr Elsevier Pub.

Matthies et .11. July 2, 1929 Mauerhoff July 28, 1931 Heidenhain Jan. 3,1939 Nassau July 4, 1939 Downing et a1. Nov. 28, 1944 Lowe et a1. Sept.12, 1950 FOREIGN PATENTS France Jan. 30, 1952 OTHER REFERENCES (30., NewYork, page 294.

1. A LIGHT SENSITIVE SILVER HALIDE PHOTOGRAPHIC EMULSION, CONTAINING APROTAMINE AS A SENSITIZING AND ACCELERATING AGENT.